Benefitting multi-enzyme system for the purpose of improving the flow properties of waxy oil

Abstract

The research work encompasses the potential of hydrocarbon-degrading recombinant enzymes for improving the flow properties of a Malaysian waxy oil. During transportation in pipeline, waxy oil has a tendency to lose its flowability due to heat loss and deposited in the pipeline, causing major production loss. Chemicals were injected proactively at production platform to counter the problem via modulation of the wax flow properties. However, chemicals are not highly effective. Enzymatic degradation of hydrocarbon was vastly studied for bioremediation of hydrocarbon-polluted sites but its application for wax treatment was limitedly reported. This concept worth a feasibility study as an alternative to chemical treatment. In this study, Malaysian waxy oil was treated with both chemical and recombinant enzymes, and the resulting effect on oil flow properties was discussed. First, treatment of oil with chemical yielded a reduction in pour point by 1–2 °C and viscosity by 11–46%. Next, a newly proposed set of recombinant enzymes identified from a modified alkane metabolism pathways were mixed as a multi-enzyme system and brought to reaction with oil in a shaking incubator at a controlled temperature, reaction time and agitation speed, resulted in reduction of pour point (3–5 °C) and viscosity (19–40%). Nonpolar solvent was added to selected enzyme formulations to overcome the hydrophobicity of the waxy oil. A better decrement in pour point (5–9 °C) and viscosity (25–79%) were achieved when the oil was treated with 1 and 2 wt% enzyme in solvent. A carbon distribution analysis revealed 30–50% long-chain carbon fraction in enzyme-treated oil were broken down into shorter chain carbon fraction. A morphology study discovered that the sharp and dense wax crystals in untreated oil disappeared. On the contrary, the wax crystals shown a dispersed pattern after treated with enzyme, which discouraged the wax from assemble into network and precipitated. As a result, a delayed appearance of wax crystal in treated oil (60–70.1 °C) is observed in contrast to untreated oil (75 °C). Finally, chemical and enzyme treatments were compared by wax deposition behavior in a simulated pipeline assemble. Oil treated with enzyme formulation yielded a lower wax deposition rate (0.09–0.3 g/m2) as compared to chemical (0.1–0.5 g/m2) over the course of 4 hours, suggesting enzyme's role in causing the delay in wax precipitation. The preceding results demonstrate that the flow properties of waxy hydrocarbon can be improved using the proposed set of immobilized recombinant enzymes with a comparable performance to chemical, therefore it is a valuable alternative.